全新java初学者实践教程6(Java SE5.0版)
.FpeVjR'' 基本语法3
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pE %{;1i 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
7HM%Cd 7FGi+ [font="Times] 1.循环语句[font="Times]:while,do-while,for
4Bz:n ;30SnR/ [font="Times]2.分支语句[font="Times]:if-else,switch,
nb_$g@ 03 [font="Times]
5v,_ Hgh 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
jPa"|9A [font="Times]
5V@c~1\ 4.异常处理语句[font="Times]:try-catch-finally,throw
OV,t| QSSA) 实践:
XsbYWJdds [font="Times] 1.循环语句
T1=T [font="Times] while 语句
YML]pNB [font="Times]class While {
&r)[6a$fW [font="Times]public static void main(String args[]) {
G[$g-NU+ [font="Times]int n = 10;
sFV&e->AN\ [font="Times]while(n > 0) {
hU6oWm [font="Times]System.out.println("tick " + n);
!!?TkVyEyM [font="Times]n--;
BnUWg ^E [font="Times]}
VMIX=gTZ [font="Times]}
7-# [font="Times]}
#Ic)]0L [font="Times] do…while 语句
+o-jMvK9 [font="Times] class DoWhile {
bYAtUEv [font="Times]public static void main(String args[]) {
.W
s\%S [font="Times]int n = 10;
w;;9YFBdM [font="Times]do {
,=V9? [font="Times]System.out.println("tick " + n);
<NXJ&xs-+ [font="Times]n--;
"."ow| [font="Times]} while(n > 0);
|wINb~trz [font="Times]}
qV79bK [font="Times]}
y~n1S~5cI 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
xM)6'= x6 [font="Times] for语句
1V.oR`&2E [font="Times] class ForTick {
?"$Rw32 [font="Times]public static void main(String args[]) {
V@rqC[on [font="Times]int n;
zd|n!3; [font="Times]for(n=10; n>0; n--)
5y8VA4L/o [font="Times]System.out.println("tick " + n);
c*.-mS~Z` [font="Times]}
@L$!hTaP [font="Times]}
dVe,;?+A 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
Q>(a JF 还有啊,[font="Times]for循环的部分可以为空的
QtQbr*q@% [font="Times]class ForVar {
=}zSj64 [font="Times]public static void main(String args[]) {
o3YW(%cYR [font="Times]int i;
C?j:+ [font="Times]boolean done = false;
[h63* & [font="Times]i = 0;
Z7XFG&@6 [font="Times]for( ; !done; ) {
Xz`0nU [font="Times]System.out.println("i is " + i);
vb6kr?-i* [font="Times]if(i == 10) done = true;
i&YWutG [font="Times]i++;
stQ_Ke [font="Times]}
%
:h%i| [font="Times]}
6=:s3I^ [font="Times]}
循环语句的例子下载 `I.pwst8i- [font="Times] 2.分支语句[font="Times]
Q_>W!)p Gz [font="Times] if/else语句
R,ZG?/#uM9 [font="Times]class IfElse {
nF
B]#LLv [font="Times]public static void main(String args[]) {
MXiQWg$ [font="Times]int month = 4; // April
dTjDVq&Hz [font="Times]String season;
9y&bKB2, [font="Times]if(month == 12 || month == 1 || month == 2)
J6Vx7 [font="Times]season = "Winter";
_"*}8{| [font="Times]else if(month == 3 || month == 4 || month == 5)
6H=gura& [font="Times]season = "Spring";
0X3yfrim [font="Times]else if(month == 6 || month == 7 || month == 8)
UmR4zGM} [font="Times]season = "Summer";
m!5Edo-;< [font="Times]else if(month == 9 || month == 10 || month == 11)
.cm2L,1h [font="Times]season = "Autumn";
z]7 /Gc,j [font="Times]else
_b$ yohQ [font="Times]season = "Bogus Month";
M|NQoQ8q [font="Times]System.out.println("April is in the " + season + ".");
XBoq/kbw! [font="Times]}
|az2vD6P [font="Times]}
)k;;O7Ck [font="Times]//这段程序输出[font="Times]:
5|5p -B [font="Times]//April is in the Spring.
HuJc*op-6 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
c?N,Cd~q [font="Times] switch语句
#_{Q&QUk [font="Times] class Switch {
}R11G9N. [font="Times]public static void main(String args[]) {
WdH/^QvTP [font="Times]int month = 4;
qVfl6q5 [font="Times]String season;
K)U[xS;< [font="Times]switch (month) {
T<-_#}.Hn [font="Times]case 12:
Ss%1{s~ok [font="Times]case 1:
~Up{zRD"B [font="Times]case 2:
4(p`xdr}K [font="Times]season = "Winter";
zy5FO<-> [font="Times]break;
n*Uk<_WA [font="Times]case 3:
.G#li(NWH [font="Times]case 4:
hD=.rDvO [font="Times]case 5:
bF6J>&]! [font="Times]season = "Spring";
}wkY`" [font="Times]break;
<v'&Pk< [font="Times]case 6:
)U=]HpuzI [font="Times]case 7:
]IE Z?+F, [font="Times]case 8:
<z\ `Ma [font="Times]season = "Summer";
?U{<g,^ [font="Times]break;
^GyZycch [font="Times]case 9:
2,wwI<=E' [font="Times]case 10:
N<1+aL\ [font="Times]case 11:
<Se9aD [font="Times]season = "Autumn";
\5 rJ [font="Times]break;
'NZ=DSGIy [font="Times]default:
+:"0%( [font="Times]season = "Bogus Month";
J>5 rkR@/ [font="Times]}
G bclR:G [font="Times]System.out.println("April is in the " + season + ".");
$dF3@(p [font="Times]}
G:p85k` [font="Times]}
分支语句代码下载 0Ni{UV?
k 8xg^="OJ [font="Times]switch语句适合于条件非常多的逻辑
1)MDnODJ 请看上述语句可以混合使用,请看
下载例子